Dnsmasq trouble with Linksys MR9000

dnsmasq does not work.
@NoTengoBattery did pre-install dnsmasq and some more services.
NoTengoBattery v3.0.3 r16554-1d4dea6d4f

openwrt-21.02 branch (git-21.188.55099-e52e1de)

But when i add something like server=/twitch.tv/ in the dnsmasq.conf and restart dnsmasq service / reboot device, then nothing changed and still every website is available.
Do i have to enable dnsmasq somewhere ? Do i have to disable adblock ?

What i what to do is a whitelist-system, that block every page, except the pages on the whitelist.
Dnsmasq did this job well on my old Router.
On my old Router i had dnsmasq 2.80, now it's 2.85..

Thank you for your help <3

Do you know for a fact the clients are using your dns?